1. Field of the Invention
The present invention relates generally to mobile communication systems, and in particular, to a power amplifier for a mobile communication system. More particularly, the present invention relates to a power amplifier for a mobile communication system where the power amplifier has a power divider at an input end and a power combiner at an output end for improving linearity thereof.
2. Description of the Related Art
In a code division multiple access (CDMA) mobile communication system, a mobile station and a base station each have a power amplifier for amplifying a received low-power signal or a transmission signal to a desired power level. A typical power amplifier for a CDMA mobile station or base station includes multiple amplifiers arranged in a cascaded design configuration having several stages. The overall performance characteristic of such a cascaded design configuration for the multiple amplifiers therefore depends mainly on the amplifier providing a final output signal, i.e., the final amplifier. Therefore, even though the amplifiers in the leading stage have a good characteristic, if the final amplifier has a poor characteristic, the overall performance characteristic of the power amplifier is adversely affected.
Accordingly, the final amplifier is designed to increase linearity, i.e., to cause the final output signal of the power amplifier to be linearly proportional to an input signal of the power amplifier. To achieve such a result, there is generally an increase in the amount of current consumed by the final amplifier which inevitably causes an increase in power consumption of the mobile station. The increase in power consumption leads to a decrease in a run-time (or life time) of a battery for the mobile station. Accordingly, the base station in radio communication with the mobile station also experiences an increases in power consumption. Therefore, there is a demand for a power amplifier which reduces the current consumption while maintaining linearity, even if the cascaded design configuration of multiple amplifiers is not used.